Biorefineries producing green chemicals from renewable resources offer an alternative to oil refineries based on dwindling supplies of petroleum and permit a move towards improved energy security. Lignocellulosic residues from forestry and agriculture are attractive as feedstocks, since they are abundant, relatively inexpensive, and are not used for food. Lignocellulose consists mainly of lignin and two classes of polysaccharides, cellulose and hemicellulose. The polysaccharides can be hydrolyzed to sugars which can be used as a platform chemical for the production of a host of other chemicals, for example by fermentation of the sugars in to various fermentation products, such as bioalcohols. The fermentation processes utilizes fermenting agents to convert the sugar in to fermentation products. One such fermenting agent is baker's yeast (Saccharomyces cerevisiae) which can be used to ferment sugars in to ethanol. The hydrolysis of cellulose is typically preceded by a pretreatment, in which the hemicellulose is degraded and the cellulose is made increasingly accessible to cellulolytic enzymes.